      
function setImagePreview() {  
        var docObj = document.getElementById("ctl00_ContentMain_file_head");  
        var fileName = docObj.value;  
        if (!fileName.match(/.jpg|.gif|.png|.bmp/i)) {  
            alert('您上传的图片格式不正确，请重新选择！');  
            return false;  
        }  
  
        var imgObjPreview = document.getElementById("preview");  
        if (docObj.files && docObj.files[0]) {  
            //火狐下，直接设img属性  
            imgObjPreview.style.display = 'block';  
            imgObjPreview.style.width = '63px';  
            imgObjPreview.style.height = '63px';  
            //imgObjPreview.src = docObj.files[0].getAsDataURL();  
            if (window.navigator.userAgent.indexOf("Chrome") >= 1 || window.navigator.userAgent.indexOf("Safari") >= 1) {  
                imgObjPreview.src = window.webkitURL.createObjectURL(docObj.files[0]);  
            }  
            else {  
                imgObjPreview.src = window.URL.createObjectURL(docObj.files[0]);  
            }  
        } else {  
            //IE下，使用滤镜  
            docObj.select();  
            docObj.blur();  
            var imgSrc = document.selection.createRange().text;  
            var localImagId = document.getElementById("localImag");  
            //必须设置初始大小  
            localImagId.style.width = "63px";  
            localImagId.style.height = "63px";   
            //图片异常的捕捉，防止用户修改后缀来伪造图片  
            try {                  
                localImagId.style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale)";  
                localImagId.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = imgSrc;  
            } catch (e) {  
                alert("您上传的图片格式不正确，请重新选择！");  
                return false;  
            }  
            imgObjPreview.style.display = 'none';  
            document.selection.empty();  
        }  
        return true;  
    }    